| Objective: To study the knee angle,maximum effective velocity,kinematics and dynamics parameters of the men’s high level tennis athletes at Beijing sports university,using Qualisys infrared motion capture device and Kistler portable 3D measuring platform,to explore the influence and causes of different kneeling angles on serving speed,and to provide reference for the professional tennis players to optimize the lower leg movement.Methods: Eight high-level male tennis players from Beijing Sport University were selected as experimental subjects.The subject made 15 effective internal corners to make a strong flat serve.After completing the first five serve,the tester asked the subject to make five effective powerful serves with lower and higher squat and knee flexion positions.The portable 3D force plate was used to record the reaction force of the subject’s field direction(Fx)and vertical ground direction(Fz),and the Qualisys motion capture system was used to record the joint’s joint angle,center of gravity position,etc.at different knee flexion angles.The radar speed gun will record the subject’s effective serve speed.SPSS 19.0 statistical software was used to analyze the data of each group by one-way analysis of variance,and the kinematics and dynamic parameters were analyzed by Spearman or Pearson correlation with the ball speed.Results: 1.According to the maximum knee flexion angle of the left knee of each serving action recorded by the motion capture system,divide all angles into three groups according to <90°,90°-100°,> 110°.The ball speed(186.17 ± 8.11 km /h)of the knee angle > 110° group was significantly higher than that of the 90°-110°group(177.88 ± 10.47 km / h)and the <90° group(180.10 ± 8.97 km / h).2.The vertical explosive power(503.07 ± 246.83 W)of the knee angle> 110° group is significantly higher than that of the 90°-110° group(1105.68 ± 182.30 W)and <90°group(1236.23 ± 184.55 W).The Z-axis explosive force is significantly related to the ball speed.r = 0.24.3.The X-axis center-of-gravity displacement(0.70 ± 0.08 m)of the knee angle > 110° group was significantly higher than that of the 90°-110° group(0.55 ± 0.06 m)and the <90° group(0.53 ± 0.06 m),X The axial center-of-gravity displacement was significantly correlated with the ball speed,r = 0.19;the knee angle was> 110°,and the left knee angle 169.98 ± 4.82°)at the lowest point of the racket was significantly higher than the 90°-110° group(160.37 ± 11.77 °)and the <90°(145.78 ± 12.53°),the left knee angle at the lowest point of the racket is significantly related to the ball speed,r = 0.28;the right elbow angle(114.77 ± 4.79 °)膝 is significantly lower than the 90°-110 ° group(129.36 ± 7.87 °)and <90° group(128.89± 9.25)°,the right elbow angle is significantly related to the ball speed,r =-0.18;knee angle> 110> group,the height of the center of gravity of the Z axis(0.99 ± 0.07)m is significantly higher than 90°-In the 110° group(0.87 ± 0.08)m and the <90°group(0.80 ± 0.05)m,the center of gravity of the Z axis was significantly related to the ball speed,r = 0.38.Conclusion: 1.The angle of the knee joint in the serve lead stage has effect on the speed of the vigorously serve ball,when the angle of the knee joint in the lead stage is greater than 110°,the serve speed is faster.2.Maximum knee bending moment the knee angle may affect the serve speed by affecting the size of the Z shaft pedal extension force,the greater the explosive force,the faster the ball speed.3.Maximum knee bending moment knee angle affects the serve speed by affecting the knee angle and the height of the Z axis center of gravity when the pedal reaches the lowest point of the racket. |
PDF Full Text Request